Described herein are blends comprising a biphenyl containing poly(aryl ether sulfone) and a poly(aryl ether ketone). These blends have limited miscibility and excellent mechanical compatibility. These blends possess, in an article molded therefrom, a good balance of properties including higher modulus, impact resistance, solvent resistance and resistance to environmental stress cracking.
Poly(aryl ether ketones) offer an exceptional balance of properties; namely, high melting point, excellent thermal stability, excellent hydrolytic stability, high stiffness and strength, good toughness, and excellent solvent and environmental stress rupture resistance. However, the high melting point (&gt;300.degree. C.) of poly(aryl ether ketones) seriously limits the number of polymeric systems which can be considered for blending. Further, the somewhat low glass transition temperature (Tg) of these materials (&lt;170.degree. C.) limits their use in several applications such as composites, bearings and seals, and electrical connectors. This is primarily because of the loss in modulus as the Tg is traversed.
Polymer blends have been widely taught and employed in the art. As broad as this statement may be, the blending of polymers remains an empirical art and the selection of polymers for a blend giving special properties is, in the main, an Edisonian-like choice. Certain attributes of polymer blends are more unique than others. The more unique attributes when found in a blend tend to be unanticipated properties.
(A) According to Zoller and Hoehn, Journal of Polymer Science, Polymer Physics Edition, vol. 20, pp. 1385-1397 (1982)
"Blending of polymers is a useful technique to obtain properties in thermoplastic materials not readily achieved in a single polymer. Virtually all technologically important properties can be improved in this way, some of the more important ones being flow properties, mechanical properties (especially impact strength), thermal stability, and price. PA0 . . . Ultimately, the goal of such modeling and correlation studies should be the prediction of blend properties from the properties of the pure components alone. We are certainly very far from achieving this goal." PA0 "The aromatic polyether ketone may be blended with other thermoplastic polymeric substances, for example, polyesters, polyolefins, polyamides, polysulfones, and poly(vinyl chloride). The composition may be further mixed with particles; e.g., elastomeric materials and polytetrafluoroethylene." PA0 hydroquinone, PA0 4,4'-dihydroxybenzophenone, PA0 4,4'-dihydroxybiphenyl, and PA0 4,4'-dihydroxydiphenyl ether. PA0 4-(4-chlorobenzoyl)phenol, PA0 4,4'-difluorobenzophenone, PA0 4,4'-dichlorobenzophenone, PA0 4-chloro-4'-fluorobenzophenone, ##STR7## PA0 (a) a mixture of substantially equimolar amounts of PA0 (b) at least one aromatic monoacyl halide of formula EQU H--Ar"--COW PA0 where --Ar"-- is a divalent aromatic radical and H is an aromatically bound hydrogen atom, Y is halogen, and COY is an aromatically bound acyl halide group, which monoacyl halide is self-polymerizable, and PA0 (c) a combination of (a) and (b) in the presence of a fluoroalkene sulphonic acid.
In the field of miscibility or compatibility of polymer blends, the art has found predictability to be unattainable, even though considerable work on the matter has been done. According to authorities:
(B) "It is well known that compatible polymer blends are rare." Wang and Cooper, Journal of Polymer Science, Polymer Physics Edition, vol. 21, p. 11 (1983).
(C) "Miscibility in polymer-polymer blends is a subject of widespread theoretical as well as practical interest currently. In the past decade or so the number of blend systems that are known to be miscible has increased considerably. Moreover, a number of systems have been found that exhibit upper or lower critical solution temperatures, i.e., complete miscibility only in limited temperature ranges. Modern thermodynamic theories have had limited success to date in predicting miscibility behavior in detail. These limitations have spawned a degree of pessimism regarding the likelihood that any practical theory can be developed that can accommodate the real complexities that nature has bestowed on polymer-polymer interactions." Kambour, Bendler, Bopp, Macromolecules, 1983, 16, 753.
(D) "The vast majority of polymer pairs form two-phase blends after mixing as can be surmised from the small entropy of mixing for very large molecules. These blends are generally characterized by opacity, distinct thermal transitions, and poor mechanical properties. However, special precautions in the preparation of two-phase blends can yield composites with superior mechanical properties. These materials play a major role in the polymer industry, in several instances commanding a larger market than either of the pure components." Olabisi, Robeson and Shaw, Polymer-Polymer Miscibility, 1979, published by Academic Press, New York, N.Y., p. 7.
(E) "It is well known that, regarding the mixing of thermoplastic polymers, incompatibility is the rule and miscibility and even partial miscibility is the exception. Since most thermoplastic polymers are immiscible in other thermoplastic polymers, the discovery of a homogeneous mixture or partially miscible mixture of two or more thermoplastic polymers is, indeed, inherently unpredictable with any degree of certainty, for example, see P. J. Flory, Principles of Polymer Chemistry, Cornell University Press, 1953, Chapter 13, page 555." Younes, U.S. Pat. No. 4,371,672.
(F) "The study of polymer blends has assumed an ever-increasing importance in recent years and the resulting research effort has led to the discovery of a number of miscible polymer combinations. Complete miscibility is an unusual property in binary polymer mixtures which normally tend to form phase-separated systems. Much of the work has been of a qualitative nature, however, and variables such as molecular weight and conditions of blend preparation have often been overlooked. The criteria for establishing miscibility are also varied and may not always all be applicable to particular systems." Saeki, Cowie and McEwen, Polymer, 1983, vol. 24, January, p. 60.
Blends of poly(aryl ether ketones) and poly(aryl ether sulfones) have been briefly alluded to in the patent literature. British Pat. No. 1,446,962 (page 3, lines 28 to 32) states
This disclosure generally describes blends of poly(aryl ether ketones) and poly(aryl ether sulfones). However, the above-quoted statement contains so many inaccuracies that it is, in essence, not relevant. Blending poly(vinyl chloride) at temperatures &gt;300.degree. C. would give instantaneous degradation yielding large quantities of hydrochloric acid as well as other noxious by-products. Polyolefins, polyesters (e.g., poly(ethylene terephthalate), poly(butylene terephthalate) and polyamides (e.g., nylon 6, nylon 6,6, nylon 11, and nylon 12) also will severely degrade at processing temperature in excess of 300.degree. C. and thus produce useless blends with poly(aryl ether ketones).
U.S. Pat. No. 3,324,199 describes blends of a specific poly(aryl ketone) containing ortho hydroxy groups (relative to the ketone group). These materials are described as ultraviolet light stabilizers for a variety of polymers including polyethylene, polypropylene, poly(vinyl chloride), poly(vinylidene chloride), polyacrylic acid esters, polyacrylonitrile, polyvinyl fluoride, polyvinylidene fluoride, polytetrafluoroethylene, polychlorotrifluoroethylene, polyesters, polyamides, and polyimides. These poly(aryl ketones) are generally amorphous and require aromatic hydroxyls ortho to the main chain ketones. The poly(aryl ketones) of this invention are crystalline, have no ortho hydroxyls, and could not be blended with many of the above mentioned polymers as the melting point of the poly(aryl ether ketones) are higher than the degradation temperature of most of the above cited polymers.
It has been found that the reaction product of biphenol and 4,4'dichlorodiphenyl sulfone (biphenol based polysulfone) exhibits an interesting property balance and exhibits a limited level of miscibility in blends with poly(aryl ether ketones). The level of intermixing is at least partially responsible for the excellent mechanical properties exhibited by the blend. Other poly(aryl ether sulfones) containing biphenyl have been found to exhibit similar characteristics in blends with poly(aryl ether ketones).